Add account balance anchors

web/src/Accounts.tsx

@@ -1244,9 +1244,16 @@ function AccountEditor({
                 pattern="[A-Z]{3}"
                 maxLength={3}
                 value={value.currency}
-                onChange={(e) =>
-                  setValue({ ...value, currency: e.target.value.toUpperCase() })
-                }
+                onChange={(e) => {
+                  const currency = e.target.value.toUpperCase();
+                  setValue((current) => ({
+                    ...current,
+                    currency,
+                    ...(currency !== current.currency
+                      ? { anchor_balance: "", anchor_date: "" }
+                      : {}),
+                  }));
+                }}
               />
             </Field>
           </div>
@@ -1288,11 +1295,40 @@ function AccountEditor({
           >
             <input
               value={value.external_account_id || ""}
-              onChange={(e) =>
-                setValue({ ...value, external_account_id: e.target.value })
-              }
+              onChange={(e) => {
+                const external = e.target.value;
+                setValue((current) => ({
+                  ...current,
+                  external_account_id: external,
+                  ...(external !== (current.external_account_id || "")
+                    ? { anchor_balance: "", anchor_date: "" }
+                    : {}),
+                }));
+              }}
             />
           </Field>
+          {value.anchor_date && (
+            <Field
+              label="Balance anchor"
+              hint="The bank's booked balance, captured once after a sync. It fixes this account's start balance on Wealth. Clear it and the next synchronization captures a fresh one."
+            >
+              <div className="anchor-row">
+                <span>
+                  {money(value.anchor_balance ?? "0", value.currency)} on{" "}
+                  {value.anchor_date}
+                </span>
+                <button
+                  type="button"
+                  className="button subtle"
+                  onClick={() =>
+                    setValue({ ...value, anchor_balance: "", anchor_date: "" })
+                  }
+                >
+                  Clear anchor
+                </button>
+              </div>
+            </Field>
+          )}
           <label className="checkbox">
             <input
               type="checkbox"

web/src/Wealth.tsx

@@ -309,8 +309,11 @@ export default function WealthPage({
                     <dt>Completeness</dt>
                     <dd>
                       Cash equals the real balance only when the journal holds
-                      that account's full history: a broker export does, a
-                      date-windowed bank statement does not.
+                      that account&rsquo;s full history: a broker export does, a
+                      date-windowed bank statement does not. A connected bank
+                      account closes that gap with an anchor — the bank&rsquo;s
+                      own booked balance, captured once — from which the start
+                      balance before the recorded rows is derived.
                     </dd>
                   </div>
                 </dl>
@@ -547,7 +550,10 @@ function AssetsPanel({
           </p>
         </div>
         <div className="row-actions">
-          <button className="button secondary" onClick={() => setEditing(blank)}>
+          <button
+            className="button secondary"
+            onClick={() => setEditing(blank)}
+          >
             <Plus size={16} />
             Add asset
           </button>

web/src/api.ts

@@ -11,6 +11,11 @@ export interface Account {
   // against: a broker export carries no counterparty, so its deposits and
   // withdrawals pair with the funding account through this IBAN.
   reference_iban?: string;
+  // anchor_balance is the bank's booked balance on anchor_date, captured once
+  // from open banking after a sync. It fixes the start balance of a
+  // date-windowed history; clearing both lets the next sync re-anchor.
+  anchor_balance?: string;
+  anchor_date?: string;
   active: boolean;
 }
 // Instrument is a security held in an investment account. The ISIN is the

web/src/styles.css

@@ -2675,3 +2675,9 @@ footer span:first-child {
     font-size: 10px;
   }
 }
+.anchor-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 8px;
+}